This invention relates to a temperature controller for electric cooking appliances, particularly to one adjustable in a horizontal direction in a wide range of temperature with many stages of heat to be used for cooking.
Nowadays electric cooking appliances are mostly popular, such as frying pans, baking pans, ovens, etc. and provided with an electric heater as shown FIG. 1, which includes a heat transformer A1, a fix contact point A2, and a plate spring A3. The heat transformer A1 has a projection A4 on its end, and the contact point A2 is located between the heat transformer A1 and the plate spring A3. Further, a movable contact point A5 is provided on the plate spring 3 corresponding to the fix contact point A2 and the end of the plate spring A3 is near the projection A4 of the heat transformer A1. When this conventional heater is turned on, the fix contact point A2 and the movable contact point A5 contacts each other to let current through. As the temperature rises higher and higher in the heater, the heat transformer A1 is gradually disfigured to grow bigger and bigger until the heater reaches a certain temperature, then the projection A4 contacts the end of the plate spring A3 and pushes it forward, separating the movable contact point A5 from the contact point A2 to turn off the power. Next, as shown in FIG. 2, when the temperature of the cooking appliance falls down gradually and the heat transformer recovers its original shape, with the projection A4 retreating back to let the plate spring A3 move back to its original position, permitting the movable contact point A5 contact again the fix contact point A2 to turn on again the heater. This the most simple structure of the heater in the conventional electric cooking appliances.
Then a conventional temperature controller shown in FIG. 3 is additionally provided in conventional electric cooking appliances, having a turning button B1 for adjusting different temperature for cooking different foods. The turning button B1 includes a shaft B2 fixed with the button B1 located on an outer surface of an electric cooking appliance, and the shaft B2 has its end connected to one side of the plate spring A3. When the turning button B1 is rotated to force a male threaded section B21 of the shaft B2 rotate and move along a female threaded section of a fixing member B3 to the most front point, the plate spring A3 is moved by the shaft B2 with the largest push force so that the plate spring A3 transforms to force the movable contact point A5 automatically separate from the contact point A2. Then at this position, the temperature is set as OFF, with the power being in turned-off condition.
If the turning button B1 is turned to let the shaft B2 retreat, the shaft B2 is reduced in its push force, and the plate spring A3 also moves back to let the movable contact point A5 contact again the fix contact point A2 to turn on power to heat up. The temperature to be heated up depends on the push force of the plate spring A3. For example, if the shaft B2 is retreated only a little as shown in FIG. 4, the push force of the plate spring A3 is reduced only a little, so the projection A4 may contact the plate spring A3 to let the movable contact point A5 separate from the contact point A2 to turn off the power in case the heat transformer A1 disfigures only a little. Then the temperature is adjusted in the medium degree. If the shaft B2 is retreated to the farthest back as shown in FIG. 5, the shaft B2 does not push the plate spring A3, which then has no push force, and the power will not be turned off until the heat transformer A1 is heated up to disfigure to a the largest degree. Then the temperature is adjusted the highest, with the turning button B1 turned for more than 270 from the OFF point.
Some conventional electric cooking appliances use a temperature controller by means of linear movement of an activate rod instead of the turning button B1 just described, owing to their shape, as shown in FIG. 6. As the activating rod C cannot rotate the shaft B2, it uses a connect rod C1 for attaining the purpose. The activating rod C has a guide slot C2 in its inner end and the connect rod C1 has one end pivotally connected to the guide slot C2 and the other end fixed with the end of the shaft B2. Then the activating rod C is moved horizontally to rotate the shaft B2 forward or backward to set the temperature needed.
But the conventional temperature controller using this activating rod has the problem as follows. The limited length of the activating rod C restricts the swinging angle of the connect rod C1 within 180, so the rotating angle of the shaft B2 is limited within 180 so that the range of temperature adjustable is also limited, impossible to set a wide range of temperature as can as that using the turning button B1.